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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 8, August 2017, pp. 833–840, Article ID: IJCIET_08_08_086

Available online at http://http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=8&IType=8

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

TANGENTIAL STRESS FACTOR

COMPUTATION IN POINT MOUNTED

STRUCTURAL GLASS

B. Venkatesh

Department of Aerospace Engineering, RVCE, Bangalore, India

Gowtham Reddy G


Benjamin Rohit


Syed Sharin,

Department of Mechanical Engineering, PESIT-BSC, Bangalore, India

ABSTRACT

The main objective in this study is to compute the stress factors when the effect of

countersinking a hole comes into play in comparison with the stress factors computed

for a cylindrical straight bolt hole in accordance with DIN 18008-3. FEM analysis

using 3-D volume elements were done with the commercially available software

Abaqus. The study was carried out for various dimensional parameters of point

mounted glass. This study has also carried out parametric sensitivity analysis for a

single counter-sunk bolt hole and a double counter-sunk bolt to compute the increase

in the tangential stress factor values when changing over from a straight cylindrical

hole to a countersunk and a double countersunk hole. It was found that the stress

factors increase when the hole is countersunk.

Key words: DIN 18008-3, Counter-Sunk Bolting, Double Counter-Sunk

Cite this Article: B. Venkatesh, Gowtham Reddy G, Benjamin Rohit and Syed

Sharin, Tangential Stress Factor Computation in Point Mounted Structural Glass,

International Journal of Civil Engineering and Technology, 8(8), 2017, pp. 833–840.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=8

1. INTRODUCTION

Glass is a highly brittle material but also an eco-friendly material used for construction of

buildings to allow sunlight for lighting the interiors. But since it is highly brittle safety is

always a point of concern. It is very difficult to analyze crack growth and crack propagation.

B. Venkatesh, Gowtham Reddy G, Benjamin Rohit and Syed Sharin


Hence it is very much necessary to know the limits to which the stresses can be produced in

the glass material. There is a lack of knowledge when it comes to simple design tools during

the use of structural glass. This study deals with the development of efficient and linear tool

for the design of glass bolting in point supported glass in accordance with DIN18008-3

standard norms. The support conditions have been advanced for different type of boltings. As

there is less work done in this field, there is very less literature available for point mounted

glass in accordance with DIN 18008-3.

2. DIN 18008-3 – COMPUTATION OF STRESS FACTORS.

Technical Experiment for Point mounted Glazing. For standard DIN 18008:2010-12 the

design value (limit stress) depends on the type of the glass. The maximum limit stress for

thermally toughened glass is given by

��,� = ��, .�

�� (�)

Where,

� : Construction Factor

��,� : Characteristic limit stress value

�� : Partial Factor

Maximum limit stress for a glass which is not thermally toughened,

��,� = ��, .�

�� . �� (�)

Where, �� is the correction factor.

Now we will be discussing the stress factors due to the loading and at the bore of a point

supported glazing. The stresses are calculated using the simplified method of the linear

superposition of local and global stress components as shown in equation.

�� =��

��.��

��

. ��. �� (�)

Where,

�� : Stress factor for Force ��

�� : Reference thickness as per DIN 18008-3

�� : Thickness of the glass

�� : Shear Force

!� = ��",� + ��,� + ��,� + . �$,� (%)

Where,

!� : Design value of Loading

��",� : Local Stress component resulting from the normal force in Z direction

��,� : Local Stress component resulting from the shear force in XY direction

��,� : Local Stress component resulting from the Bearing Torque

. �$,� : Stress Factor k and Global stress component

At the present this is only available for cylindrical hole bolting. We would like to expand

this methodology to countersunk bolting and check for the increase in safety factors between

cylindrical and countersunk holes.

Tangential Stress Factor Computation in Point Mounted Structural Glass


Figure 1 Glass bolt model in accordance with St. Venant’s principle [2]

Stresses in the glass plate follow the Saint-Venant’s Principle [Fig 1] which is evaluated

only at a sufficiently large distance from the loading point. The global structural behaviour of

the plate is taken by the global stress component. The local region is defined as a circular area

cantered at each bore section surrounding the respective point holder. The radius of the sphere

is three times the Bore diameter as shown in the figure. �$ = �$. �&� �� (� = ��) (')

Here we use FEM to study and calibrate the stresses to obtain the b-factors used in design

for the countersunk bolting.

2.1. Hex mesh Vs Tet mesh

In this analysis we have chosen hex mesh over tet mesh because of the reason that hex mesh

have a higher degree of freedom than that compared to a tet mesh which provide a more

accurate and practical results compared to a tet mesh.

2.1.1. Mesh Sensitivity

We tried to put obtain the simulation results by increasing the mesh density along the edge of

bolt by increasing the number of nodes. By plotting the results we find that the values of the

stress factors converge to the DIN 18008-3 values [Fig 2]. In the test simulation cases we

have applied a load of 1000N at an angle of 74° in the plane of shear lateral to the shank.

Figure 2 Convergence to actual DIN value with increasing mesh density



2.1.2. Contact angle between bolt shank and hole

A study on varying stress was done by applying a constant load by varying the angle in the

plane of shear. We found that the Equivalent stress tend to increase at low angles and start

decreasing as the angle of application of load is increased.

2.2. Stress factors for cylindrical bolted holes

We have verified the results by attaining consistency with the values for cylindrical glass bolt.

[2]

Table 1 Variation of stress factors with the bolt bore diameter

S.NO Bore diameter(mm) DIN

Values

FEM

Results

Deviation

from DIN

values

1 20 3.13 3.11 0.02

2 25 3.92 3.9 0.02

3 30 4.7 4.68 0.02

4 35 5.48 5.46 0.02

5 40 6.26 6.24 0.02

6 45 7.05 7.07 0.02

7 50 7.83 7.85 0.02

8 55 8.31 8.33 0.02

3. STRESS FACTORS FOR COUNTER-SUNK AND DOUBLE

COUNTER-SUNK BOLT

We have used FEM modelling and simulation using commercially available software

Abaqus[3]

for the counter-sunk bolt [Fig 3] to predict the stress factors in shear stress

conditions [Table 2]. In this the friction due to the contact between the bolt and the glass face

is not considered. This could also add to the deviation. It is not in the scope of this paper to

consider friction. We have done analysis in considerations with Von-Mises stress [Fig 4].

Figure 3.General dimension of the counter-sunk hole[4]

Figure 4 FEM Analysis of counter-sunk hole#



Table 2 Shear stress factors obtained from simulation for counter-sunk hole

S.NO Bore diameter(mm)

DIN Values

for Cylindrical

bolts

FEM Results

for Cylindrical

bolts

FEM Results

for counter-

sunk bolts

Percentage

increase in

Stress factor

1 20 3.13 3.11 5.33 41.65

2 25 3.92 3.9 8.16 52.2

3 30 4.7 4.68 11.68 59.99

4 35 5.48 5.46 16.44 66.7

4 40 6.26 6.24 22.01 71.65

5 45 7.05 7.07 28.37 75.07

6 50 7.83 7.85 35.65 77.98

7 55 8.31 8.33 43.74 80.95

3.1. Effect of varying angle of counter-sunk

We then carried out variation in the parameter - angle of countersunk. We carried out this

variation for a fixed bore diameter of 45mm maintaining constant thickness of the glass plate.

Figure 5 Parametric sensitivity on angle of counter-sunk

3.2. Influence of the variation of shank in counter-sunk hole

Varying the height of the counter-sunk hole region, we try to obtain the values for stress

factors for the different values of the parameters.

Figure 6 Parametric sensitivity of shank of counter-sunk hole



3.3. Stress factors for double counter-sunk bolts

We simulate and obtain the shear stress factors [Table 3] for varying diameter of the bore by

giving double axis symmetry in ‘x’ as well as in ‘z’ direction.

Figure 7 General dimensions of Double counter-sunk bolt

Figure 8 FEM analysis of double counter-sunk bolt

Table 3 Stress Factors for double counter-sunk bolts

S.NO Bore

diameter(m)

DIN Values

for

Cylindrical

bolts

FEM

Results for

Cylindrica

l bolts

FEM

Results for

counter-

sunk bolts

Percentag

e increase

in Stress

factor

FEM

Results

for double

counter-

sunk bolts

Percentag

e increase

in Stress

factor

1 20 3.13 3.11 5.33 41.65 6.21 49.91

2 25 3.92 3.9 8.16 52.2 9.57 59.24

3 30 4.7 4.68 11.68 59.99 15.14 69.08

4 35 5.48 5.46 16.44 66.7 21.56 74.67

5 40 6.26 6.24 22.01 71.65 32.64 80.08

6 45 7.05 7.07 28.37 75.07 40.84 82.68

7 50 7.83 7.85 35.65 77.98 52.57 85.03

8 55 8.31 8.33 43.74 80.95 65.31 87.24

4. RESULTS AND DISCUSSIONS

Glass is a material which is of late being used in construction, despite the fact that there is

lack of official standards and guidelines which can give details on design procedures and

material strength characteristics. The oldest design principle is based on the factor of safety

(fallowable = frupture/fos)[4]

. Here we use the same principle to check the magnitude of FOS



required while using a countersunk bolting. As there are no standard values for a countersunk

bolting in DIN 18008-3, we try to obtain stress factors for countersunk bolting to account for

the increase in the safety factor when changing from cylindrical bolting to counter-sunk

bolting and also when changing to double counter-sunk bolting we see the maximum stress

factors induced in it.

Equivalent stresses are found to be maximum in Double counter-sunk bolt. The maximum

stress is found to occur in two different regions as shown [Fig 8].This is mainly because of the

reason being that there is more surface in the inclined or angular region of the counter-sunk or

double counter-sunk bolt which induces higher stress in the shank.

We can note that as the bolt hole is being counter-sunk the degree of difference increases

quadratically and tends to be linear in case of a cylindrical bolt, this phenomenon has to be

studied in detail to be able to get a better understanding.

Table 4 Shear stress factors of Counter-sunk bolting

dT [mm]

Hole Diameter(d) [mm]

20 25 30 35 40 45 50 55

bfxy bfxy bfxy bfxy bfxy bfxy bfxy bfxy

50 6.21 9.57 - - - - - -

55 6.21 9.57 15.14 - - - - -

60 6.21 9.57 15.14 21.56 - - - -

65 6.21 9.57 15.14 21.56 32.64 - - -

70 6.21 9.57 15.14 21.56 32.64 40.84 - -

75 6.21 9.57 15.14 21.56 32.64 40.84 52.57 -

80 6.21 9.57 15.14 21.56 32.64 40.84 52.57 43.74

Table 5 Shear stress factors Double Counter-sunk bolting

dT [mm]

Hole Diameter(d) [mm]

20 25 30 35 40 45 50 55

bfxy bfxy bfxy bfxy bfxy bfxy bfxy bfxy

50 5.33 8.16 - - - - - -

55 5.33 8.16 11.68 - - - - -

60 5.33 8.16 11.68 16.44 - - - -

65 5.33 8.16 11.68 16.44 22.01 - - -

70 5.33 8.16 11.68 16.44 22.01 28.37 - -

75 5.33 8.16 11.68 16.44 22.01 28.37 35.65 -

80 5.33 8.16 11.68 16.44 22.01 28.37 35.65 65.31



5. CONCLUSION

Figure 9 Comparing the different type of bolts

From the results obtained [Table 4] and [Table 5] above we conclude that the cylindrical

bolts are more efficient in handling higher stresses, even when comparing cylindrical bolts

with a normal counter-sunk bolt and the double counter-sunk bolts the cylindrical bolts are the

ones which dominate as the stresses induced in them is less [Fig 9]. But at the same time the

counter-sunk bolts are not exposed to the outer environment and are always within the surface

of the glass whereas the cylindrical bolts protruding out and hence tend to spoil the outlook of

the self-supporting skins. Therefore we can note that to have better looking structure with

counter-sunk bolts we have to increase the margin of safety as indicated above. Hence there

always exists a negotiable approach in choosing the appropriate bolt for the need and to

satisfy the purpose.

REFERNCES

[1] Mark Porter, Aspects of Structural Design with Glass, Balliol College and the Department

of Engineering Science,The University of Oxford, 2001

[2] Technische Regeln für die Bemessung und Ausführung punktförmig gelagerter

[3] Verglasungen (TRPV), Schlussfassung August 2006,

[4] DS Simulia. Abaqus Scripting Manual 6.14.

[5] Benjamin Rohit, Neel Sagar, Supreeth R, Dandapani P, Computation of Stress Factors for

Counter-Sunk Bolt Fixings in Self Supporting Skins in accordance with DIN 18008-3,14th

International Conference on Developments in Science, Management and Engineering, 14th

& 15th April 2017

[6] D. Rajesh, V. Balaji, A. De varaj and D. Yogaraj, An Investigation on Effects of Fatigue

Load on Vibration Characteristics of Woven Fabric Glass/Carbon Hybrid Composite

Beam under Fixed-Free End Condition using Finite Element Method. International

Journal of Mechanical Engineering and Technology 8(7), 2017, pp. 85–91

[7] B. Anjaneyulu, G. Nagamalleswara Rao, Dr. K. Prahladarao and D. Harshavardhan.

Analysis of Process Parameters in Milling of Glass Fibre Reinforced Plastic Composites.

International Journal of Mechanical Engineering and Technology, 8(2), 2017, pp. 149–

159.

tangential stress factor computation in … · din 18008-3 – computation of stress factors....

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